ABSTRACT
Objective:To construct the molecular transmission network of human immunodeficiency virus type 1 (HIV-1) epidemic strains in northern Zhejiang Province (Jiaxing City and Huzhou City) and to explore the HIV-1 transmission characteristics in this region.Methods:A total of 371 newly diagnosed human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) patients in Jiaxing City and Huzhou City in 2017 were included as study subjects, and the blood samples were collected and the basic demographic and epidemiological information were obtained. RNA in plasma was extracted, and the pol region gene sequence was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) and nested polymerase chain reaction (PCR) to construct phylogenetic tree for identifying subtypes. The pairwise genetic distances were calculated, and the optimal threshold of genetic distance was selected, and finally the molecular transmission network was constructed. Chi-square test was used for statistical analysis. Results:The pol region gene sequences of 336 samples were successfully obtained, and 11 subtypes were detected, mainly including circulating recombinant form (CRF)07_BC (40.8%, 137/336) and CRF01_AE (31.2%, 105/336). Based on the 1.0% genetic distance threshold, the molecular transmission network of HIV-1 was plotted. A total of 38 transmission clusters (cluster sizes ranging from two to 28) including 119 patients were found, with males predominantly (82.4%, 98/119) and most of the patients aged over 40 (include 40) years old (52.9%, 63/119), mainly infected with CRF07_BC subtype (57.1%, 68/119) and CRF01_AE (24.4%, 29/119). The clustering rate of CRF07_BC (49.6%, 68/137) was significantly higher than that of CRF01_AE (27.6%, 29/105), the difference was statistically significant ( χ2=5.27, P=0.022). Two large clusters C1 (28 cases) and C2 (11 cases) were identified, the majority of which were men who have sex with men (17 cases and seven cases, respectively). High-risk cases generally sought sexual partners in local or nearby cities through mobile phone dating software, of which the infected sequences mostly had high homology with other economic developed regions (Guangdong Province, Beijing City and Hangzhou City, etc.). Conclusions:The HIV-1 subtypes are diverse in Jiaxing City and Huzhou City, mainly CRF07_BC and CRF01_AE. The HIV-1 transmission networks are complex, among which high-risk cases may be the key factor leading to the HIV-1 epidemic in the region. Therefore, it is urgent to deepen the transmission network monitoring and formulate timely precise intervention and prevention strategies.
ABSTRACT
Objective@#Using field epidemiological investigation and molecular analysis to construct the molecular transmission network of human immunodeficiency virus/acquired immunodeficiency syndrome cases (HIV/AIDS) newly diagnosed in Huzhou in 2017, Zhejiang Province.@*Methods@#A total of 160 participants were obtained through a web-based system from Chinese Center for Disease Control and Prevention (CCDC) with the features of diagnosed in Huzhou in 2017 who also had been collected samples for the first follow-up. The basic information of demographic characteristics and risk factors was extracted from the website. RNA was extracted from plasma samples of untreated cases, followed by RT-PCR and nest-PCR for pol gene amplification, sequencing. Phylogenetic tree was constructed by MEGA software for HIV gene subtyping. TN93 model was used for calculating the distance between two sequences. Cytoscape software was used for drawing molecular transmission network. And then an epidemiological survey was conducted to cases in the primary cluster.@*Results@#A total of 138 sequenced individuals (86.3%) were acquired from 160 individuals. Among which, 123 (89.1%) were male. The highest proportion of subtype was CRF07_BC (60, 43.5%), followed by CRF01_AE (46, 33.3%), and with four cases of Unique Recombinant Form (URF, CRF01_AE and CRF07_BC) and one case of URF (subtype B and C). A total of 18 molecular clusters included 56 individuals (40.6%) were found in the transmission network under the optimal genetic distance threshold (1.0%). The clustering proportion of CRF07_BC (66.1%, 37 cases) was higher than that of CRF01_AE. There were 9 clusters formed among CRF07_BC, including 37 cases (accounting for 61.7%, 37/60). The primary transmission cluster contained 11 cases, among which 9 cases were transmitted by homosexual sex. The first time of the cases to have homosexual behavior is range from 2010 to 2016, whose media number (P25, P75) of partners was 6 (3.5, 8.5). Most of the cases come from Anhui Province and engaged in garment industry (5 cases), between which there were 8 cases used Blued software to seek for casual partners, 1 case seeking for casual partners in garden.@*Conclusion@#With CRF07_BC and CRF01_AE predominantly circulating, HIV genetic diversity had been noticed in this area. The primary cluster was consisted of high proportion of locally new infections, and a specific population aggregation in limited place existed.